Well its not a book but I use MIT's lecture material for supplementary notes MIT OpenCourseWare | Free Online Course Materials
Is it ok to ask on here about sourcing PDF copies of textbooks?
I'm living in Thailand and my books are back in the UK and I was wanting to brush up on my skills to take some more courses. I've completed MU123, MST121, and a part of MS221. I'd love to have copies of the textbooks to look over.
Or if anyone have an recomendations on where to look for public domain for the same level work that would be great.
You might try Mathvids. You can download, for free, many videos on math topics from K6 to Calculus, and a few on subjects usually studied after Calculus. Some of their vids are from MIT OCW, which Shakarri . You'll find some texts you can download, too.
Other than that, if you really do want texts, the best I can suggest is to search for some specific math terms, like trigonometry or combinatorics. A search for "mathematics" is too broad.
I know of a couple of good downloadable texts for calculus and linear algebra, but I gather you're not there yet.